CN109935821B

CN109935821B - SiO (silicon dioxide)xPreparation method of-G/PAA-PANI/graphene composite material

Info

Publication number: CN109935821B
Application number: CN201910268492.5A
Authority: CN
Inventors: 任玉荣; 廖远红; 陈智慧; 刘振
Original assignee: Changzhou University
Current assignee: Changzhou University
Priority date: 2019-04-04
Filing date: 2019-04-04
Publication date: 2022-02-11
Anticipated expiration: 2039-04-04
Also published as: CN109935821A

Abstract

The invention relates to SiO_xThe preparation method of the-G/PAA-PANI/graphene composite material comprises the following steps: (a) performing ball milling treatment on the SiO; (b) carrying out heat treatment on graphite; (c) mixing the treated SiO and graphite, and performing ball milling in inert gas atmosphere to obtain SiO_x-a graphtite mixture; (d) dissolving polyacrylic acid in an alkaline solution, and subsequently adding the SiO_xCarrying out ultrasonic agitation on the graphtite mixture to obtain a first mixed solution; (e) and adding an aniline monomer and a cross-linking agent into the first mixed solution, carrying out polymerization reaction under an ice bath condition, then adding a graphene dispersion solution, and carrying out aging, standing, dialysis and drying. Therefore, the mechanical strength of the lithium battery is utilized to buffer the volume expansion of the silicon-based material and effectively improve the conductivity, and the prepared lithium battery has the advantages of low cost, good cycle performance and the like.

Description

SiO (silicon dioxide)xPreparation method of-G/PAA-PANI/graphene composite material

Technical Field

The invention belongs to the field of lithium battery cathode materials, relates to a cathode composite material, and particularly relates to a SiO_xA preparation method of the-G/PAA-PANI/graphene composite material.

Background

With the rapid development of science and technology, the requirements on power/energy are higher and higher; in the research in the lithium ion battery field, silicon as the lithium ion battery cathode material has very high theoretical specific capacity (4200mAh g)^-1) It is believed that it is most likely to replace conventional graphite (about 370mAh g)^-1) One of the materials of the negative electrode. However, silicon has two problems: firstly, the conductivity is not strong; secondly, in the charging and discharging process, the volume expansion of the silicon material reaches up to 300 percent, so that the silicon material is pulverized and falls off from the upper surface of the current collector. Thus, the cyclic performance of silicon materials is the biggest issue that needs to be overcome at presentOne of the problems is.

In recent years, the modification of SiO materials has received attention from researchers, and SiO also has a relatively high theoretical specific capacity (about 1300mAh g)^-1) It has been reported that silicon oxide is more stable than elemental silicon in terms of volume expansion during charge and discharge, but still has low conductivity and also undergoes volume expansion. Chil-Hoon Doh et al tried to modify SiO and clad with a carbon layer, but when the lithium ion battery was cycled for 30 cycles, the capacity was only 688mAh g^-1. There is still room for improvement in the performance of silica-based anode materials.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide SiO_xA preparation method of the-G/PAA-PANI/graphene composite material.

In order to achieve the purpose, the invention adopts the technical scheme that: SiO (silicon dioxide)_xThe preparation method of the-G/PAA-PANI/graphene composite material comprises the following steps:

(a) performing ball milling treatment on the SiO;

(b) carrying out heat treatment on graphite;

(c) mixing the treated SiO and graphite, and performing ball milling in an inert gas atmosphere to obtain a SiOx-G compound;

(d) dissolving polyacrylic acid in an alkali solution, then adding the SiOx-G compound, and performing ultrasonic stirring to obtain a first mixed solution;

(e) and adding an aniline monomer and a cross-linking agent into the first mixed solution, carrying out polymerization reaction under an ice bath condition, then adding a graphene dispersion solution, and carrying out aging, standing, dialysis and drying.

Preferably, in the step (a), the particle size of the SiO is 10 nm-10 μm.

Optimally, in the step (b), the temperature of the heat treatment is 400-1000 ℃, the time is 10-30 min, and the protective gas is argon.

Optimally, in the step (c), the mass ratio of the SiO to the graphite is 1: 0.2 to 2.

Further, in the step (c), the rotation speed of the ball mill is 400-600 rpm, the time is 5-8 h, and the ball-to-material ratio is 25-35: 1.

Preferably, in step (d), the alkali solution is an aqueous solution containing one or more of sodium hydroxide, potassium hydroxide, sodium carbonate and potassium carbonate.

Further, in the step (d), the concentration of the alkali solution is 0.2-1.0 mol/L.

Optimally, the mass ratio of the polyacrylic acid to the aniline monomer is 1:1 to 30.

Further, the SiO_xThe mass ratio of the-G compound to the aniline monomer is 1-10: 1.

optimally, the graphene dispersion and SiO_xThe mass ratio of the-G compound is 1-5: 100.

due to the application of the technical scheme, compared with the prior art, the invention has the following advantages: SiO of the invention_xAccording to the preparation method of the-G/PAA-PANI/graphene composite material, a three-dimensional network structure formed by physical actions such as hydrogen bonding between acrylic macromolecules and hydrogen bonding between aniline macromolecules is fully utilized through the doping action of polyacrylic acid on polyaniline, so that the mixed hydrogel with polyaniline and volume phase change performance is obtained, and a synergistic effect is generated with doped graphene to ensure the volume expansion of the buffering silicon-based material and effectively improve the conductivity, so that the prepared lithium battery has the advantages of low cost, good cycle performance and the like.

Drawings

FIG. 1 shows SiO based on the preparation obtained in example 1_x-battery cycling performance map of G/PAA-PANi/graphene composite;

FIG. 2 shows SiO based on the preparation obtained in example 1_x-charge and discharge curves of G/PAA-PANi/graphene composite;

FIG. 3 shows SiO based on the preparation obtained in example 1_x-CV plot of G/PAA-PANi/graphene composite;

FIG. 4 is SiO obtained in example 1_x-transmission electron and scanning electron micrographs of G/PAA-PANi/graphene composite: (a) SEM images before testing; (b) SEM images after testing; (c) a pre-test TEM image; (d) TEM images after testing; (e) food made of glutinous rice flour(j) An EDS map;

FIG. 5 is SiO obtained in example 1_x-XPS plot of G/PAA-PANi/graphene composite;

FIG. 6 shows SiO obtained in example 1_xFT-IR plot of G/PAA-PANI/graphene composite.

Detailed Description

SiO of the invention_xThe preparation method of the-G/PAA-PANI/graphene composite material comprises the following steps: (a) performing ball milling treatment on SiO (partial Si-O bonds can be broken and partial Si particle clusters exist, so that the graphite after heat treatment can be effectively coated on the surface of the silicon monoxide material in the high-energy mechanical ball milling mixing process, and simultaneously the disorder degree of the compound can be increased, thereby being beneficial to improving the performance of the compound material); (b) carrying out heat treatment on graphite; (c) mixing the treated SiO and graphite, and performing ball milling in an inert gas atmosphere to obtain a SiOx-G compound; (d) dissolving polyacrylic acid in an alkali solution, then adding the SiOx-G compound, and performing ultrasonic stirring to obtain a first mixed solution; (e) and adding an aniline monomer and a cross-linking agent into the first mixed solution, carrying out polymerization reaction under an ice bath condition, then adding a graphene dispersion solution, and carrying out aging, standing, dialysis and drying. Through the doping effect of polyacrylic acid on polyaniline, a three-dimensional network structure formed by physical effects such as hydrogen bonding effect between acrylic macromolecules and hydrogen bonding effect between aniline macromolecules is fully utilized, so that the mixed hydrogel with polyaniline and volume phase change performance is obtained, and a synergistic effect is generated with doped graphene to ensure the volume expansion of the buffering silicon-based material and effectively improve the conductivity, so that the prepared lithium battery has the advantages of low cost, good cycle performance and the like.

In the step (a), the particle size of the SiO is 10 nm-10 μm. In the step (b), the temperature of the heat treatment is 400-1000 ℃ (preferably 600 ℃, the heating rate is 5-10 ℃/min), the time is 10-30 min, and the protective gas is argon. In the step (c), the mass ratio of SiO to graphite is 1: 0.2 to 2; preferably 1: 1. in the step (c), the rotation speed of the ball mill is 400-600 rpm, the time is 5-8 h, and the ball-to-material ratio is 25-35: 1. in step (d)The alkali solution is an aqueous solution containing one or more of sodium hydroxide, potassium hydroxide, sodium carbonate and potassium carbonate; the concentration of the alkali solution is 0.2-1.0 mol/L. The mass ratio of the polyacrylic acid to the aniline monomer is preferably 1: 1-30, preferably 1:16, and the mass ratio of the SiOx-G compound to the aniline monomer is preferably 1-10: 1, optimally 2.5: 1. the cross-linking agent is conventional, such as selected from ammonium persulfate and FeCl₃And H₂O₂And the like, in an amount conventionally selected (usually 0.05 to 1% by mass of the monomer to be polymerized). The graphene dispersion liquid and SiO_xThe mass ratio of the-G compound is preferably 1-5: 100.

the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings:

example 1

The present embodiment provides a SiO_xThe preparation method of the-G/PAA-PANI/graphene composite material comprises the following steps:

(a) taking 6g of commercially available SiO, ball-milling for 6h (with argon as protective gas), wherein the rotation speed is 500rpm, and the ball-material ratio is 30: 1;

(b) placing 6g of graphite in a tube furnace, heating from room temperature to 600 ℃ at the speed of 5 ℃/min in the argon atmosphere, preserving heat for 10min, and naturally cooling to room temperature;

(c) taking the graphite subjected to heat treatment and the SiO subjected to ball milling according to the mass ratio of 1:1, ball milling for 6 hours (the rotating speed is 500rpm, the ball material ratio is 30: 1) to obtain SiO_x-a G complex;

(d) dissolving 0.005g polyacrylic acid in water, swelling in an oven at 60 deg.C for 1h, and adding 0.5ml sodium hydroxide solution (concentration of 0.5 mol/L); then the SiO prepared in step (c) is added_xAdding a-G compound (0.2G), performing ultrasonic treatment for 1h, and stirring in an ice bath to obtain a first mixed solution;

(e) adding 0.08g of aniline monomer and ammonium persulfate solution (0.5ml, concentration of 0.001mol/L) into the first mixed solution, and reacting for 20min in an ice bath; then adding 0.002g of graphene dispersion liquid (commercially available, avadin, 0.002g/ml), and aging for 24 h; dialyzing for 24h, pre-freezing for 6h, and freeze-drying for 12h to obtain SiO_x-G/PAA-PANi/gGraphene composite material (namely graphene doped conductive hydrogel modified SiO)_x-composite material of graphite, SiO for short_x-G/PAA-PANi/graphene)。

SiO to be prepared_xthe-G/PAA (polyacrylic acid) -PANI (polyaniline)/graphene composite material is used for assembling the button cell (2032 type button cell) to carry out electrochemical performance test. Active Substance (SiO) at the following weight ratio_x-G/PAA-PANi/graphene composite): conductive agent (acetylene black): 75% of binder (sodium alginate): 10%: grinding 15% of the mixture evenly, coating the mixture on a current collector (copper foil), cutting the mixture into a wafer with the diameter of 14mm after natural drying, drying the wafer in vacuum at 105 ℃ for 8h, taking a metal lithium sheet as a counter electrode, and 1mol/L LiPF₆The electrolyte (the solvent is EC: DC: DEC with 10% of FEC added according to the volume ratio of 1: 1: 1) and Celgard2300 are diaphragms, and the assembly is completed in a glove box filled with argon to prepare the CR2032 button cell. Performing electrochemical performance test on a blue test cabinet (CT2100A), wherein the voltage range is 0.01-3V, and the current density is 500mA g^-1。

FIG. 2 shows SiO composite material of example 1_xThe charge-discharge curve diagram of-G/PAA-PANI/graphene shows that the first discharge specific capacity is 1420.8mAh G^-1The first charging specific capacity is 1062.3mAh g^-1(ICE 74.77% of specific capacity in initial discharge) and a current density of 500mA g^-1. The irreversible capacity can be attributed to the first delithiation-lithiation with SEI film formation and Li and SiO_xA chemical reaction between them. FIG. 1 shows the cycling stability of the material from cycle 8 to cycle 100 (SiO-based materials were also used)_xBased on SiO_xAssembling the cathode material of G/PAA-PANI into a battery for performance comparison); the coulombic efficiency based on the composite material in example 1 was always about 99%, at 500mA g^-1The specific discharge capacity after 100 times of circulation under the current density is 842.3mAh g^-1. And based on SiO_xThe initial specific discharge capacity of the battery (only adopting SiO as an active material) reaches 1916.6mAh g^-1The capacity suddenly decreases due to the breakage of the SiO structure. With SiO_xComparison of-G/PAA-PANI composite materials (i.e., no graphene dispersion added in example 1)For comparison), SiO_x-The G/PAA-PANI/graphene composite material has higher capacity, which not only improves the conductivity of the conductive hydrogel, but also improves the mechanical strength of the conductive hydrogel, and also means that SiO is generated_x-G is surrounded by a three-dimensional structure PAA-PANI and interpenetrates SiO_x-G units. Fig. 3 is a cyclic voltammogram of the negative electrode material. A relatively flat reduction peak at 1.2V occurred in the first cycle, corresponding to decomposition of the electrolyte, e.g. FEC, according to previous studies. At 0.7V with concomitant SEI formation. One of the important reasons why the electrode capacity is not completely reversible is that SiO_xProducts formed by chemical contact with Li, including Li₂O and Li₂Si₂O₅It is irreversible. This is because the chemical reaction between Li and graphite is between 0V and 0.25V, while Li₂O and silicates made of SiO_xAnd Li between 0.25V and 0.6V; this is also reflected in the appearance of the cathodic peak at the oxidation peak of 0.2V indicating Li vs Li_xC separation from Li_xThe voltage position of Si-detached Li was 0.6V.

FIG. 4(a) is SiO without charge and discharge test_xSEM image of G/PAA-PANI/graphene. As can be seen from FIG. 4(a), SiO_xThe grain size of the-G/PAA-PANI/graphene ranges from tens of nanometers to microns. After ball milling, SiO_xIs significantly reduced in size. The heat treated graphite becomes more fluffy and thus more completely coated in SiO_xOn the surface of (a). FIG. 4(b) is SiO after 100 cycles_xSEM image of-G/PAA-PANI/graphene showing that the morphology of the material does not collapse after passing through the cycle, which indicates that the connection of the 3D network structure PAA-PANI formed after crossing effectively adapts to the volume change of the silicon material during the cycle, and that the PAA-PANI conductive hydrogel with flexibility and mechanical strength is effectively coated on SiO_x-on the surface of G. As can be seen from FIG. 4(c), graphene is distributed on SiO_x-G/PAA-PANi perimeter, which plays a supporting connection in the structure and can improve the electrical conductivity of the performance; the conductive hydrogel with deformability and flexibility is also uniformly coated on the SiO_x-on the surface of G. After the electrochemical performance test of FIG. 4(d), a large number of dispersed quantum dots were formed on the surface of the substrateAdapting Si and Li in the internal structure of the material₂O makes a great contribution in volume expansion; FIGS. 4(e) to 4(j) are SiO solid layers obtained in example 1_xEDS diagram of G/PAA-PANI/graphene composite. The Si 2p spectrum represents five valence states of Si: SiO (99.98eV, 15.55%), Si¹⁺(102.06eV，20.11％)，Si²⁺(102.85eV，29.63％)，Si³⁺(103.68eV, 29.63%) and Si⁴⁺(105.00eV, 5.08%); the average valence of Si calculated from the Si 2p spectrum was 1.88. From the C spectrum it can be seen that: c, C-O and C-N bound by Sp2 are located at 286.75eV, and C ═ O is located at 288.8 eV; from the N spectrum, a strong peak at 400.00 eV is present, corresponding to the characteristic chemical bond N-H of PANi. Protonated amines of doped PAA were centered at 402.20eV and 403.70 eV (as shown in figure 5). FIG. 6 is SiO_xFourier Infrared (FT-IR) spectrum of G/PAA-PANI/graphene. At 3430cm^-1、2920cm^-1、1720cm^-1And 1090cm^-1The absorption peak at (A) corresponds to the N-H bending vibration absorption peak, -CH₂-a stretching vibration absorption peak, a C ═ O bending vibration absorption peak and a C — H bending vibration absorption peak, several of which are sufficient to demonstrate the presence of PAA. 1400cm^-1～1650cm^-1Is a characteristic peak of polyaniline, and the absorption peak is weaker. 1440cm^-1is-CH₂Bending vibration absorption Peak of 1490cm^-1Is benzene type C ═ C stretching vibration absorption peak, and the quinone type C ═ C is 1580cm^-1And 1630cm^-1Is the bending vibration absorption peak of N-H.

Example 2

The present embodiment provides a SiO_x-G/PAA-PANi/graphene composite material, substantially in accordance with example 1, except that: in the step (c), the graphite and the ball-milled SiO are mixed according to the mass ratio of 1: 2, mixing.

Example 3

The present embodiment provides a SiO_x-G/PAA-PANi/graphene composite material, substantially in accordance with example 1, except that: in the step (c), the graphite and the ball-milled SiO are mixed according to the mass ratio of 5: 1, mixing.

Example 4

The present embodiment provides a SiO_x-G/PAA-PANi/graphene composite material, substantially in accordance with example 1, except that: in step (b), the temperature was raised from room temperature to 400 ℃ at a rate of 5 ℃/min in an argon atmosphere.

Example 5

The present embodiment provides a SiO_x-G/PAA-PANi/graphene composite material, substantially in accordance with example 1, except that: in step (b), the temperature is raised from room temperature to 1000 ℃ at a rate of 5 ℃/min in an argon atmosphere.

Example 6

The present embodiment provides a SiO_x-G/PAA-PANi/graphene composite material, substantially in accordance with example 1, except that: the mass ratio of the SiOx-G compound to the polyacrylic acid to the aniline monomer is 2.5: 1: 1.

example 7

The present embodiment provides a SiO_x-G/PAA-PANi/graphene composite material, substantially in accordance with example 1, except that: the mass ratio of the SiOx-G compound to the polyacrylic acid to the aniline monomer is 9: 0.1: 1.6.

example 8

The present embodiment provides a SiO_x-G/PAA-PANi/graphene composite material, substantially in accordance with example 1, except that: in the step (e), the amount of the graphene dispersion liquid added was 0.01 g.

Example 9

The present embodiment provides a SiO_x-G/PAA-PANi/graphene composite material, substantially in accordance with example 1, except that: in step (e), the amount of graphene dispersion added was 0.005 g.

Comparative example 1

This example provides a method of preparing a composite material, which is substantially the same as in example 1, except that: no polyacrylic acid was added.

Comparative example 2

This example provides a method of preparing a composite material, which is substantially the same as in example 1, except that: aniline monomer and ammonium persulfate were not added.

Comparative example 3

This example provides a method of preparing a composite material, which is substantially the same as in example 1, except that: in the step (c), the graphite and the ball-milled SiO are mixed according to the mass ratio of 1: 5, mixing.

Cells were assembled by the specific procedures of example 1 using the negative electrode composites of examples 1 to 9 and comparative examples 1 to 3, and electrochemical tests were performed, the results of which are shown in table 1.

TABLE 1 tables of battery performances of negative electrode composite assemblies in examples 1 to 9 and comparative examples 1 to 3

The above embodiments are merely illustrative of the technical concept and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the content of the present invention and implement the invention, and not to limit the scope of the invention, and all equivalent changes or modifications made according to the spirit of the present invention should be covered by the scope of the present invention.

Claims

1. SiO (silicon dioxide)_xThe preparation method of the-G/PAA-PANI/graphene composite material is characterized by comprising the following steps of:

(a) performing ball milling treatment on the SiO;

(b) carrying out heat treatment on graphite; the temperature of the heat treatment is 400 ℃ or 600 ℃, the time is 10-30 min, and the protective gas is argon;

(c) mixing the treated SiO and graphite, and performing ball milling in inert gas atmosphere to obtain SiO_x-a G complex;

(d) dissolving polyacrylic acid in an alkali solution, then adding the SiOx-G compound, and performing ultrasonic stirring to obtain a first mixed solution; the aqueous alkali is an aqueous solution containing one or more of sodium hydroxide, potassium hydroxide, sodium carbonate and potassium carbonate, and the concentration of the aqueous alkali is 0.2-1.0 mol/L;

2. SiO as claimed in claim 1_xThe preparation method of the-G/PAA-PANI/graphene composite material is characterized by comprising the following steps: in the step (a), the particle size of the SiO is 10 nm-10 μm.

3. SiO as claimed in claim 1_xThe preparation method of the-G/PAA-PANI/graphene composite material is characterized by comprising the following steps: in the step (c), the mass ratio of SiO to graphite is 1: 0.2 to 1.

4. SiO according to claim 1 or 3_xThe preparation method of the-G/PAA-PANI/graphene composite material is characterized by comprising the following steps: in the step (c), the rotation speed of the ball mill is 400-600 rpm, the time is 5-8 h, and the ball-to-material ratio is 25-35: 1.

5. SiO as claimed in claim 1_xThe preparation method of the-G/PAA-PANI/graphene composite material is characterized by comprising the following steps: the mass ratio of the polyacrylic acid to the aniline monomer is 1:1 to 30.

6. SiO as claimed in claim 5_xThe preparation method of the-G/PAA-PANI/graphene composite material is characterized by comprising the following steps: the mass ratio of the SiOx-G compound to the aniline monomer is 1-10: 1.

7. SiO as claimed in claim 1_xThe preparation method of the-G/PAA-PANI/graphene composite material is characterized by comprising the following steps: the mass ratio of the graphene dispersion liquid to the SiOx-G compound is 1-5: 100.